Chloroplast polypeptide composition of rice plants {Oryza sativa L. cv. Safari) exposed for 30 d to increasing Cu ion concentrations in a hydroponie growth medium was analyised. The conventional discontinuous SDS-aerylamide gel electrophoretic systém, the SDS PhastGel (Pharmacia Fine Chemicals) gradient 10-15 and tíie 5-8 pH range polyaciylamide isoelectric focusing of the PhastSystem separation and development technique were ušed. With Cu levels greater than 0.25 g m'^ die polypeptide bands with apparent molecular masses of 42/41, 33/32, 21/20 and 19/18 kDa deereased in the PhastSystem separation and development systém, whereas with the conventional discontinuous SDS buffer systém gel electrophoresis all these bands disappeared except the 33/32 kDa band. Also, under the latter systém excess Cu deereased the 56/55, 55/54, 26 and 22 kDa bands which was not shown by the PhastSystem separation and development technique. Furthermore, in the discontinuous SDS-PAGE high Cu levels induced the disappearance of the 16.5, 14.5 and 12 kDa bands, which were again not shown by the PhastSystem separation and development technique; yet the opposite oceurred with the 49 kDa band of the gel profiles. Polyacrylamide isoelectric focusing of thyiakoid membranes showed in all Cu treatments two major bands at pl 7.7 and <5 and a minor one at pl 6.48. At Cu concentrations lower than 1.25 g m'^ two additional smáli bands appeared (pl 5.5 and 5.18); and at Cu concentrations greater than 0.25 g m'^ these smáli bands were replaced by four different ones (pl 6.7, 6.05, 5.35, 5.25).
The influence of higher temperatures on the polypeptide composition of thylakoid membranes and pigment-protein complexes, as well as on some parameters of their functional activity, in both acclimated and non-acclimated young pea plants, was studied. Almost the whole set of polypeptides in thylakoid membranes as vvell as in T40 particles was preserved after heat treatment (5 h, 55 °C). During acclimation of the plants to high temperatures a reorganization of the photosynthetic apparatus took plače. In its thylakoids the oligomer/monomer ratio of the photosystem (PS) 2 light- harvesting antenna was more than 50 % higher compared to similar samples of the non-acclimated plants. After both the treatment of 5 h at 55 °C only (non-acclimated plants) and that with step-wise increasing temperatures (acclimated plants), the PSI activity was practically unchanged in all three variants, whereas the PS2 activity decreased more significantly in non-acclimated plants only.
Morphological and ultrastructural changes, the chlorophyll (Chl) content and Chl a fluorescence induction were studied in primary leaves of runner beán plants (Phaseolus coccineus L. cv. Pi?kny Jaš) grown in Knop solution and treated with excess Cu [20 g(CuS04 x 5 H2O) m"^] at difíerent growth stages. The plants were exposed to the metal for 12 d. Cu added to the nutrient solution at the beginning growth stage induced significant leaf area reduction (31 %) as well as increase of Chl accumulation (148 %) and leaf density (122 %). No ultrastructural changes of chloroplasts were seen. Application of Cu at the advanced growth stage caused relatively smáli changes except local disturbances in stroma lamellae and leaf reduction to 70 % of control. Significant disorganization of chloroplast ultrastructure, smáli leaf area reduction (80 %) but specific leaf area increase (163 %) and leaf density decrease (67 %) were seen only in the primary leaves of plants treated with Cu at the finál stage of growth. These changes, similar to senescence response, were accompanied by Fy/Fo ratio decrease to 67 % in comparison with control.
Two new nematodes, Paraseuratoides ophisterni gen. et sp. n. (Seuratoidea: Quimperiidae) and Philometra ophisterni sp. n. (Dracunculoidea: Philometridae) are described based on specimens recovered from the intestine and mesentery, respectively, of the swamp-eel Ophisternon aenigmaticum Rosen et Greenwood (Synbranchiformes: Synbranchidae) from a canal of the Papaloapan River in Tlacotalpan, State of Veracruz, Mexico. The genus Paraseuratoides is most similar to Paraseuratum Johnston et Mawson, 1940, differing from it mainly in the absence of a bulbous inflation on the anterior end of the oesophagus and in the structure of the mouth (presence of 6 spines in addition to 6 oesophageal teeth). Neoquimperia Wang, Zhao, Wang et Zhang, 1979 and Wuinema Yu et Wang, 1992 are synonymised with Ezonema Boyce, 1971 and Paragendria Baylis, 1939, respectively, and Haplonema hamulatum Moulton, 1931 is considered a junior synonym of Ichthyobronema conoura Gnedina et Savina, 1930. Philometra ophisterni (only females) is mainly characterised by minute cephalic papillae, a greatly developed anterior oesophageal bulb separated from the cylindrical part of the oesophagus, anterior extension of the oesophageal gland anterior to the nerve ring, and by the character of large caudal projections. This is the first Philometra species recorded from inland fishes in Mexico.
Problematika rotačních a valivých pohybů bývá považována studenty a často i učiteli fyziky za značně obtížnou. Plně obecné řešení problémů spojených s takovým typem pohybu (pohyb setrvačníků apod.) ovšem vyžaduje odpovídající matematický aparát, a pak je samozřejmě namístě s takovým názorem souhlasit. Na druhé straně je možné na zcela elementární úrovni, ať již středoškolské, či bakalářské, provést výklad i takových rotačních a valivých pohybů, jimž se nejen učebnice, ale i učitelé při přímé výuce raději vyhýbají. Dokladem jsou výsledky tohoto článku, jenž vychází z gymnaziálního studentského projektu z oblasti mechaniky valivých pohybů. Studuje různé aspekty valení, zejména podmínky pro valení bez prokluzu, popis valení s prokluzem a podmínky přechodu mezi nimi. Teoretické závěry jsou ověřeny pomocí jednoduchých experimentů. Data jsou zpracována pomocí softwaru Tracker, který je mimořádně vhodný pro využití na středoškolské úrovni, a poté porovnána metodou nejmenších čtverců s teortickým modelem. Ze závěrů studie je zřejmé, že úlohy uvedeného typu mohou dokonce řešit studenti velmi samostatně, samozřejmě s konzultační a materiální podporou. Na rozdíl od často viděných soutěžních prací z moderní fyziky, do jejíž podstaty středoškolský student v principu nemůže pronïknout (a práce buď zůstavá na povrchu, nebo se student stává pouhým účastníkem týmového výzkumu či pomocníkem vědeckého konzultanta), mají důsledně zpracované projekty z názornějších klasických, i když ne tak "atraktivních" oblastí fyziky zásadní význam pro prohloubení fyzikálního myšlení studentů., This paper presents results of a secondary school student project in rollng mechanics. Various aspects of rolling motions are studied, particularly conditions for rolling without slipping, a description of rolling with slipping, and conditions for transitions between the two. Theoretical results and conclusions are verified by simple experiments, the data being treated by an open source software, Tracker (appropriate for secondary school level use) and processed by the least squares method using theoretical models. It is demonstrated that rotational and rolling motions, considered difficult for students, can be treated elementarily even at the secondary school or university bachelor level and solved by students themselves and therefore demonstrate how such a project can develop their thinking., and Jiří Bartoš, Jana Musilová, Luboš Vozdecký.